5.

My codes (for computing and for plotting):

5 a.

5a.png

5 c.

num5c.png

5d and 5e.

The KE of the system along the S domain is NOT linear (bottom-left figure). The second mode just adds energy (regulated by the stratiform fraction) to the first mode.
The surface wind (bottom-right figure) is weaker when the stratiform fraction is stronger. The reason is that a strong stratiform mode cools and creates divergence at shallow levels, which counteracts the deep convective, cyclonic, mode.
5d.png